SAN FRANCISCO (Reuters) - Mozilla, the company behind  the Firefox Internet browser, will start selling ads as it tries to grab  a larger slice of the fast-expanding online advertising market.
  The company said in a blog posting on Tuesday that it has reached  out to potential corporate sponsors about its fledgling "Directory  Tiles" program, targeted at first-time users.
  Novice Firefox users now see nine blank tiles when they open up the  browser, which fill in over time with their most-visited or recently  visited websites. Now, Mozilla intends to display the most popular sites  by location, as well as sponsored websites that will be clearly labeled  as such.